Robust chemical characterization is essentially the gateway to biological safety.
A toxicological risk assessment is only as strong as the analytical data supporting it.
FDA’s September 2026 biocompatibility town hall provided a detailed look at how the Agency is evaluating chemical characterization and toxicological evidence under ISO 10993-18. The emphasis was not simply on whether testing was performed, but whether the resulting data are sufficiently representative, sensitive, and scientifically justified to support conclusions about biological safety.
That expectation reaches well beyond testing. Extraction design, analytical thresholds, device variability, unidentified chemicals, surrogate standards, supplier changes, and CRO practices can all determine whether the toxicological evidence package remains defensible.
Key highlights covered in the audio brief:
* Characterize the final finished device. Raw-material data may not adequately represent the chemistry of the manufactured and sterilized device because processing can introduce degradation products and manufacturing residuals.
* Use extraction conditions that are both conservative and clinically relevant. FDA’s examples show that an extraction can be too weak—but it can also become artificially aggressive and generate chemicals that do not reflect actual patient exposure.
* Ensure the analytical method can actually support the toxicological threshold. FDA is scrutinizing how the analytical evaluation threshold, limit of quantification, and uncertainty factors are established and justified. If the method cannot reliably detect chemicals at the required safety threshold, the toxicological conclusion becomes difficult to defend.
* Account for device-to-device variability. Analytical replicates measure instrument repeatability. Extraction replicates using separate final finished devices are needed to evaluate variability in the devices themselves.
* Do not eliminate variability through pooling. Combining extracts can dilute a high-result outlier and mask an intermittent manufacturing-related chemical exposure. FDA specifically cautioned against this practice.
* Justify unidentified chemicals and surrogate standards. FDA expects objective scientific support for how unknown constituents are quantified and why a particular surrogate standard is appropriate.
Executive takeaway
Toxicological risk assessment should not be treated as an isolated report generated at the end of biocompatibility testing.
It is the downstream interpretation of an evidence system that begins with the finished device and depends on how that device is manufactured, extracted, analyzed, quantified, and controlled over its lifecycle.
The strongest toxicological conclusion cannot compensate for weak underlying data.
Keywords
Biocompatibility, toxicological risk assessment, chemical characterization, ISO 10993-18, biological safety, analytical evaluation threshold, AET, extraction replicates, CRO oversight, supplier change control
🎧Listen to the Executive Brief for a closer look at FDA’s expectations for toxicological data, and why extraction design, analytical sensitivity, device variability, and laboratory controls can determine whether a biological safety assessment is truly defensible.
Thanks for reading Let's Talk Risk!. If you liked this post, share with others.
Note:
The audio summary was prepared using Google NotebookLM, an AI-enabled research tool. Here are a few key resources used for this analysis:
* FDA (2026). Biocompatibility Town Hall #2: Extractions for Conducting Chemical Analysis for Biocompatibility Assessment. U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH).
This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit naveenagarwalphd.substack.com/subscribe
